Example of a Startup configuration

Startup.cs

public class Startup
    // This method gets called by the runtime. Use this method to add services to the container.
    // For more information on how to configure your application, visit http://go.microsoft.com/fwlink/?LinkID=398940
    public Startup(IHostingEnvironment env)
    {
        var builder = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings.json", true, true)
            .AddJsonFile($"appsettings.{env.EnvironmentName}.json", true)
            .AddEnvironmentVariables();

        if (env.IsDevelopment())
        {
            // For more details on using the user secret store see http://go.microsoft.com/fwlink/?LinkID=532709
            builder.AddUserSecrets();
        }

        Configuration = builder.Build();
    }

    // other code
}